Pulp screen



Aug, 23, 19270 J. A. DZCKIN$ON PULP SCREEN Filed May 5, 1935 2 Sheets-Sheet l J. 'A. DICKINSON PULP SCREEN Filed May 5, 192a 2 Sheets-$heet 2 mam-m mum/1W patented Au 23, 1927.

1,639,797 UNITED STATES PATENT OFFICE,

JOHN ARTHUR DICKINSON, .OF EAST ANGUS, QUEBEC, CANADA.

PULP SCREEN.

Application filed May 3,

This invention relates .to improvements in pulp screens and while primarily designed for use with wood pulp stock is adapted to be used for any other stocks of material carried in flotation in water or other liquid.

The objects of the invention are to provide a screen of this description for separating one size of fibre or stock from another, continually discarding the different grades of stock at differentpoints.

A further object is to provide an efficient pulp screen of simple design and few wearing parts.

With the foregoing and other objects in view, hereinafter more fully referred to, the invention comprises, in combination with a vat provided with a suitable inlet, a plurality of screening units immersed in liquid to be screened with outlets for screened Z0 material at a point below the surrounding liquid whereby the flow through the screen ing units is'provided, a plurality of adjustable weirs in said vat for regulating said flow and mechanism in'combination with the flow for oscillating the screening units.

A practical embodiment of the invention is illustrated in the accompanying drawings in which like numerals of reference indicate corresponding parts in each figure and in which Figure 1 is a plan view of my improved screen,

Figure 2 is a section on the line 22 of Figure 1,

Figure 8 is a section on the line 3-3 of Figure 1,

Figure 4 is a section on Figure 1,

Figure 5 is a section .on Figure l,

Figure 6 is a section on the line 6-6 of Figure 1 showing the screen in central position, x

Figure 7 is a crosssectional view showing the screen in eccentric position.

Referring now more particularly to the drawings, in which a preferred example of my invention is illustrated, 10 designates a vat adapted to contain liquid and provided with an intake pipe 11. Within, and spaced 50 therefrom, is a weir 12 and spaced from the weir 12, adjacent the opposite end of the yet, is a second or overflow weir 13. Intermediate of these weirs are arranged a plurality of vertical screening units 14, of which any suitable number can be used, comprising screen plates 15 mounted in pairs on a frame the line 44 of the line 5 -5 of 1926. Serial No. 106,485. 1

16, the frame being closed in between the screen plates on sides. These screen plates are cut with .a suitable sized slot or mesh .to pass the required size of fibre .or stock. Inside these frames are rigidly mounted a hollow vertical shaft 17, fitted with rigid baffles 18 and equipped with ports 19., connecting the space between the screen plates with the inside of the hollow shaft and thence to a. compartment 20, which in turn connects the regulating chamber 21, ,ha-vingflan adjustable regulating weir 22 over which the screened stock is discharged into compartment 23 from which it is discharged through a pipe .24. The frames 16 .are mounted on bushings or bearings 25 carried on the upper part of vertical shaft 17, which provides a pivot on which each frame (or screen unit is carried. Adjacent the top of this frame on each side are pins 26 von which are mounted sidebars or links 2;? connecting the screening units together and retaining .them at a uniform distance apart. The links 27 are connected by means of rods :28 to eccentric .discs or cranks 29 mounted on shaft 30 and driven by the vpulley 31 in turn driven from any suitable source of power.

From the foregoing it will be seen that screening action isobtainedby the difference in the height vof the regulating weirs 22 and the over-fiow weir .13 and the maximum screening action occurs when the regulating weir is entirely removed, the full head on the screen being the difference between the over-flow weir 18 and the level of the dis- 7 charge pipe 24}. The adjusting of the weir 22 is necessary to suit each kind .of stock and to vary :the rate of vflow through the screens. An auxiliary screening action is obtained by means of the rigid bafiies 18 in combination with the oscillating motion of the screen unit. On a forward stroke the space between the screen plate ,and the bafiie is reduced, thereby causing a. displacement of water, and on the reverse stroke this same space is increased, thereby producing a partial vacuum against the battle and causing a suction of water through the screen plates, which is of great assistance in pulling the fibres of stock through the screen plates. This condition is double actingon each side of the baffles at each stroke. The arrows indicate the fiowof stock .throughithe screen plates and out through the (ports 19, tailings or rejections which will not pass the screen provided with ports at intervals therein,

plates 15 being carried over the weir 13 into the chamber 32 and discharged through the tailing pipe 33. The regulating weir 22,

being adjustable, is operated to a height to .prevent short-circuiting past the ends of the units. The spacing between these units is gradually increased in the direction of'the flow, being a minimum at the inlet end and a maximum at the outlet end. This permits the velocity of the stock to be reduced towards the discharge end and allow of a more thorough screening action where the fibre content of the liquid is a minimum. The eccentric disc 29 imparts in operation a reciprocating movement to the links 27 which in turn rocks or oscillates the screening units on their pivots thereby permitting the liquid to have a flushing action through the slots or openings in the screen plates and keeps them from becoming clogged or choked with fibre or stock rendering these plates practically self-cleaning. Under existing conditions and constructions of screens the flow of stock is continuous in one direction which tends to clog the screens. WVith my improved screen, however, the reciprocating, oscillating movement provides a flush action which prevents clogging.

As many changes could be made in the above construction and many apparently widely different embodiments of my inven tion, within the scope of the claims, constructed without departing from the spirit or scopethereof, it is intended that all matter contained in the present specification and accompanying drawings shall be interpreted in an illustrative and not in a limiting sense.

What I claim as my invention is:

1. In a pulp screen the combination with a tank or vat provided with intake and discharge pipes and having adjustable weirs therein, of a series of pivotally mounted screening units intermediate of said weirs.

2. In a pulp screen, a pivotally mounted screening unit comprising a frame, screening plates arranged in pairs on the frame, a hollow shaft for the frame, rigid baflies on the shaft and ports in the shaft designed to connect the spaces between the screening plates and the interior of said shaft,

3. In a pulp screen, a suitable frame, a screening unit, including hollow shaft bafiies rigidly mounted on the shaft, screening plates pivotally mounted on the shaft and a discharge trough communicating with said shaft.

4. In a pulp screen, the combination, with a container, of screen plates pivotally mounted in pairs therein, a hollow shaft pivotally supporting said plates, baffles rigidly mounted on the hollow shaft and ports 1 in said shaft communicating with the spaces between the plates, a commoncompartment in the containercommunicating with the hollow shafts,

5. In a pulp screen of the character described, a plurality of screen plates, hollow vertical shafts pivotally supporting said plates, ports in the shafts and battles mounted on the shafts whereby in operation in one direct-ion the space between the screen plates is reduced to cause displacement of liquid and whereby in operation in the opposite direction said space'is increased to cause a suction through said plates, mechanism for imparting an oscillating movement to said plates.

6. In a pulp screen, the combination with a vat having a'plurality of pivotally mounted oscillating screen units therein, means the combination with a vat provided with V a discharge chamber, of a series of screening units pivotally supported in the vat and means supporting the units communicating with the discharge chamber, adjustably mounted regulating weirs for the vat and the discharge chamber and means for oscillating the screening units.

9. In a device of the character described, the combination with a series of link-connected, pivotally mounted screening units,

of means-for oscillating said unit-s including an eccentric discmember, rod connections to the units and belt mechanism for operatmg said dlsc to impart an osc1llatmg movement to the link-connected screening units. '10. In advice of the character descrlbed and. incoi'nbination with a vat having a water intake and a weir member spaced from the water intake, a second weir spaced from the aforementioned weir, and discharge pipes adjacent the second weir, a receiving chamber integral with the vat and a regulating weir communicating with said chamber, a plurality of screening members pivotally mounted in the vat, mechanism for oscillating said members and means formed in said members communicating with the pulp chamber whereby the liquid-carried material passing through the screening members is delivered to the pulp-receiving chamber and whereby the liquid-carried material rejected by the screening members is discharged through the discharge outlets.

11. In a device of the character described, a hollow shaft provided with ports, a plurality of oscillating screen plates arranged in pairs on said shaft.

12. In a device of the character described and in combination, a hollow shaft spaced ports in said shaft, a plurality of oscillating screens suitably arranged and operatively associated with said shaft.

13. In a device of the character described and in combination with a tank having regulating Weirs therein and a pulp-receiving chamber provided with a regulating weir and communicating with the tank, a plurality of reciprocating, oscillating screen units in said tank and means integral with the mounting of said units communicating with the pulp-receiving chamber.

14. The combination with a plurality of pivotally mounted screen plates, link-connected to one another, of mechanism conplurality of nected to said links for oscillating the plates.

15. The combination with a plurality of screening plates pivotally mounted on a baffle-carrying hollow shaft open at one end and provided with intermediate ports, link connected to one another, of mechanism operatively connected to said links for imparting to said plates a reciprocating, rocking or oscillating movement.

16. The combination with a vat provided with a discharge chamber and regulating weirs in the vat and said chamber, of a screening units pivotally mounted on hollow trunnions and link-connected to one another, mechanism rod connections to said links for imparting to said units a reciprocating, rocking or oscillating movement.

17. In a device of the character described and in combination, a vat or the like, a hollow shaft, a plurality of screen units operatively associated with said shaft and baffles reciprocally associated with said units,

In witness whereof I have hereunto set my hand.

JOHN ARTHUR DICKINSON. 

